522 GEOLOGY OF NORTHWESTERN TEXAS. 



the roughest in the northern part of the State. The thick beds of limestone 

 and underlying clays dipping to the northwest cause high escarpments facing 

 to the southeast. 



In places in the county there are broad, level plateaus, called in this part of 

 the State "valleys," that furnish good localities for large and fertile farms. 

 The valleys along the rivers and lateral streams are broad, and are generally 

 covered with timber, and upon them are some of the largest and best farms 

 of the county. 



GEOLOGY. 



This county is entirely within the Coal Measures series. It has been stated 

 that this county belonged to the Chester group of the Sub-Carboniferous. 

 The reasons given for so stating were based upon stratigraphic reasons alone. 

 It was supposed that the conglomerate beds found on the tops of some of the 

 highest hills along the Brazos River and elsewhere were the equivalent of the 

 Millstone Grit of the Pennsylvania Coal Measures, and which is the bottom 

 of the Coal Measures in that State; and then finding heavy beds of limestone 

 lying below the conglomerate, the conclusion was reached that these lime- 

 stones were Sub-Carboniferous. After a pretty thorough examination of 

 these conglomerates I am satisfied that they are not the equivalent of the 

 Millstone Grit, and that the limestones are not Sub- Carboniferous. The fol- 

 lowing fossils were found in the vicinity of Mineral Wells, in the north- 

 eastern part of this county, which show conclusively that the formation 

 belongs to the Coal Measures: 



Anthyris subtilita, Hall; Bellerophon carbonarius, Cox; B. nodocarinatus, Hall; 

 B. crassus, Meek and Worthen; Chonetes granulifera, Owen; Chonetes mesoloba, 

 Norwood and Pratten; Gonularia crustula, White; Discina nitida, Phillips; 

 Euomphalus rugosus, Hall; Lingula wnbonata, Cox; Loxonema rugosa, Worthen; 

 Lophophyllum proliferum, McChesney; Michelina placenta?, White; Machrochei- 

 his ventricosa, Meek and Worthen; Myalina subquadrata, Swallow; Nuculana 

 obesa, White; Nuculana bellistriata , Stevens; Nucula ventricosa, Hall; Ortho- 

 ceras rushensis, McChesney; Productus cora, D'Orbigny; P. costatus, Sowerby; 

 P. longispinus, Sowerby; P. semireticulatus, Martin; Pleurotomaria sphcerulata, 

 Conrad; P. tabulata, Hall; P. broadheadi, White; P. brazosensis, Shumard ; P. 

 turbiniformis, Meek and Worthen; Retzia mormoni, Marcou; Rhynconella uta, 

 Marcou; Spirifer cameratus, Morton; S. planoconvexus, Shumard; Spirifer 

 lineatas, Martin; S. rocky montanus, Marcou; Spiriferina kentuckensis, Shumard; 

 Synocladia biseralis, Swallow: Terebr alula bovidens, Morten; and others not 

 yet determined. 



I traced the formation beyond the eastern boundary of the county, and to 

 where the Carboniferous strata was overlaid by the Cretaceous, and at the 



